Compositions based on 2, 4-dichlorophenoxyethanol for the weed control in the rice fields



United States Patent O 2,958,55 COMPOSITIONS BASED ON 2,4-DICHLOROPHEN- OXYETHANOL FOR THE WEED CONTROL IN THE RICE FIELDS stance in the sub-surface layers of the soil containing the weed seeds that are ready to germinate, and, consequently, in a higher weedkilling activity and, lastly, in an easier removal of the residues of active substance by lavement of the rice field in the usual manner.

(3) 2,4-ETN has a lower aqueous solubility than 2,4-

DES which results in a concentration of the active sub- Giovanni Pelle ini Pietro Scrivani and Araldo Bu 'ani 5 Florence, m r; aissignors to Moritecatini Societa en Except the changes m doses used q erale Per Plndustria Minemria e ,Chimica, a comm, of application of the product 1 the same as described in fion of Italy Italian Patent No. 529,529 which relates to the methods No Drawing. Filed Oct. 31, 1955, Ser. No. 619,393 of Claims riority 2 1115511511 Italy Nov. 11 1955 In F folkwmg eximples the results P fi P experlments are described for the purpose of illustrating p Chums the present invention without intent, however, to thereby This invention relates to compositions comprising 2,4- the Scope of the dlsclosure dichlorophenoxyethanol (2,4-ETN) appropriately pro- EXAMPLE 1 vided in granular form together with diluents which may 15 A comparison between the Weed control activity of havefertilizing properties, for the purpose of controlling 2,4-ETN and 2,4-DES on sprouts of Panicum crus-galli weeds (especially Panicum crus-galli) in rice fields preas a function of the stage of development of the sprouts pared for sowing or transplantation. and of the amounts used, was carried out in greenhouse The use of sodium 2,4-dichlorophenoXy-ethylsulfate tests. A number of pots containing sieved soil from a (2,4-DES) has been previously suggested for weed conrice field, were sown each with 250 Panicum crus-galli trol in rice fields (Italian Patent No. 529,529). seeds; immediately after sowing the soil was submerged We have now found that, if 2,4-dichlorophenoxyeth- 1 under 6-7 cm. of water. The treatment with the two anol is used in doses equal to lower than those of the products (at identical conditions) was carried out on oneaforementioned compound, a more rapid and complete half of the pots when the seedlings were 1 cm. high and weed control is obtained, together with a better safe-2 on the other half when the seedlings were 3 cm. high. guard for the crop. The results obtained at the end of the test are set forth We found that a preferred use of 2,4-ETN over 2,4- in Table 1.

' Table I Dosage, Height i c iri gsiiiiz h v igli i Product kgJha. 0f the Length of Length of germinated seeds Test used act. seedepigeous hypogeous 1 subst lings, part, cm. part, cm.

cm. conrotten total torted 13.45510353 2. 81110. 141 4. 86 4. 86 2 1 5. 07510. 358 0. 85410. 141 80.43 19. 57 100 2 1 4. 24410. 358 0. 45910. 141 54.17 45.83 100 4 1 3. 63210. 358 0.17810.141 47. 59 52.31 100 4 1 2. 85110. 358 0. 08010. 141 25.00 75.00 100 2 3 9. 45810. 358 132710.141 20.13 3.88 33.01 2 3 4. 80910. 358 0. 57710. 141 88.17 11.83 100 4 3 (171810.358 0. 73410. 141 87.18 3.80 90.98 2,4-ETN 4 3 3.84010.358 0.2s510.141 51.19 48. 81 100 DES for the aforementioned purpose is based on the fol- From an examination of the foregoing biometric relowing properties of 2,4-ETN: 5 sults it is evident that both products exerted a substantial (1) The product itself is active, while 2,4-DES, in 5 weedkilling activity either by hindering the growth of order to become active, requires a chemico-biological the epigeous part and the roots, or by causing morphoconversion in the soil to 2,4-dichlorophenoxyethanol. logical anomaliesand rotting of the seedlings. This results in a rapid action of 2,4-ETN on the sprout- In the case of treating the l-cm. seedlings, the higher ing weeds and in an independency of the action from activity of 2,4-dichlorophenoxyethanol, in comparison prevailing conditions, particularly from the temperature. with 2,4-DES, is particularly apparent in connection with t This fact is of primary importance because the metethe lower dose. In the case of treating the 3-cm. seedlings, ,orologic conditions at the time of sowing or transplantthe difference in the activity of the two products is still ,ingare subject to substantial variation from year to year. more apparent; in fact, in the pots treated with both (2) 2,4-ETN, used under the same conditions and at doses of 2,4-DES a number of small plants survived s 'toichiometric equivalents, has a more intensiye efliect which probably would have completed their growth cycle than 2,4-DES and a longer, lasting action which extends even if they did not reach the size of the control plants, the activity of 2,4-ETN even against more mature weed whereas practically no weed survived when 2,4-dichloro sprouts. This fact, which We determined experimentally, phenoxyethanol was used. "is of utmost importance inthe practical application of Exam le 2 'a'weed killer used for this purpose, in view of the rela- 60 p tively short period of time that normally elapses between 1 A test Was made to compare the fate of diffusion of treatment and sowing,.a11d the fact that the weed seeds and 2,4-dichlorophenoxyethancl in soil- For germinate only gradually during this period. this purpose, to a series of cylindrical glass pots, having As .a result of the higher efliciency of 2,4-dichloroan opening at the bottom and containing sieved soil of .phenoxyethanol, the doses practically used which, in case average miXtllre, Water Was fed through the bottom Until of a composition containing 2,4-DES amount to 5-40 complete saturation was obtained; any excess of water kg. of active substance/hectare for pre-sowing treatment, Was IfimOVed- 4 subsequent .to transplantation treatment or surface treat- Subsequently, The cylindrical P were Surface treated iment, can be conveniently lowered to 4-5 kg./hectare With equivalents of 20 gof dry active m l; 5 i e substance Care was taken to attain a uniform distribution. Immediately thereafter, cc. of water were introduced in all pets from above and the bottom effluents were colin a germination box in the presence of the effluent 5 of one of the soil fractions of each pot; the number of the germinated seeds is determined each day and, finally, the biometric values of the grown seedlings are determined in all experimental germination boxes.

The results obtained at the end of the test are reported in Table 2; from these results it may be deduced that, while 2,4-DES, in the operating conditions, diffused to and was active even at a 6-cm. depth and, to some extent, at 8 cm., 2,4-dichlorophenoxyethanol remained From an examination of the foregoing results it may be seen that 2,4-dichl orophenoxylethanol (2,4-ETN) exerts its full activity even when the pots are kept at a relatively low temperature, while the activity of 2,4-DES is remarkably lowered under these conditions. In contrast thereto, no substantial difference was observed between the water samples withdrawn at the surface and the subsurface samples of water that had been in contact with soil.

EXAMPLE 4 This test was made to confirm what we had previously found, namely that 2,4-ETN, because of its biochemical characteristics, can exert an immediate and complete effect, while 2,4-DES, on the contrary, requires a. converlocalized in the first 2 cm. of the soil. The eflluent was sion in the soil in order to become active.

inactive in all cases.

200 seeds of Panicum crus-galli were sown onto the Table 2 Percent of germinepigeous hypogeous abnormal Product Germination substrate ation, part, cm. part, em. seedlings percent in respect of seedlings 2,4-DES Soil withdrawn from the pot at a depth of 2 cm 54. 5 2. 09210. 07 0 100 2,4-DES Soil withdrawn from the pot at a depth of 4 cm 53 1. 94810. 07 0 100 2,4-DE Soil withdrawn from the pot at a depth of 6 cm 69 7. 31510. 22 0. 66510. 06 98. 55 2,4-DF8 o 46 8. 45610. 26 4. 54310. 24 7. 61 2,4-ETN. Soil withdrawn from the pot at a depth of 2 cm,. 45. 5 1. 59310.07 0 100 2,4-ETN. Soil withdrawn from the pot at a depth of 4 cm 60 9. 01210. 21 6.02910. 23 0 2,4-ETN. Soil withdrawn from the pot at a depth of 6 cm 55 7. 96810. 25 6. 06310. 28 1.82 2,4-E'IN- Soil withdrawn from the pot at a depth of 8 cm 56. 5 8. 46010. 24 5. 16810. 22 1. 77 Control.. Soil withdrawn from the pot at a depth of 2 cm 55 7. 08210. 26 4. 85910. 0 OontroL. Soil withdrawn from the pot at a depth of 4 cm- 56. 5 8. 06210. 24 5. 23010. 26 0 ControL. Soil withdrawn from the pot at a depth of 6 cm. 53. 5 8. 41610. 28 4. 70510. 22 0 Oontrol Soil withdrawn from the pot at a depth of 8 cm 51. 5 8. 89810. 27 4. 46610. 22 0 2,4-DES Filter paper impregnated with efiiucnt 61. 5 7. 34510. 23 4. 84510. 18 0 2,4-ETN do 57. 5 7. 53010. 20 4. 26510. 18 0 Contr d0 62. 5 7. 87210. 18 3. 34410. 15 0 EXAMPLE 3 surface of sieved S011, contained in a senes of pots.

In a test carried out in a conditioned room, the residual weedkiller activity of the steeping water of pots containing nice field soil previously treated with 2,4-DES and with 2,4-ETN in form of a granular composition, 40

kg./ha. and the soil was then immediately submerged under 5 cm. of water. One half of the pots were incubated at 19-20 C. and the other at 10-l5 C. 10 days after the treatment, samples of the steeping water of each pot were withdrawn (at the higher level and in contact with the soil) and contacted with Panicum crusgalli seeds placed in a germination box.

The results are reported in the following table:

Table 3 TESTS CARRIED OUT 10 DAYS AFTER THE TREATMENT [(a) Pots incubated at 10l5 0.]

Epigeous hypogeous Percent of part (cm.) part (cm.) abnormal seedlings Control:

surface H 0 3. 30 5. 45 0 subsurface Hi0 2. 97 5.18 0 2,4-DES:

surface H O 2. 3. 94 35. 13 subsurface H20 2. 60 3. 38 36. 2,4-ETN:

surface H2O 2.04 0.64 91. 42 subsurface Hi0 1. 89 1.09 78. 78

[(12) Pets incubated at 1924 0.]

Control:

surface H2O 3. 29 5. 20 subsurface H2O 3. 22 4. 88 2,4-DES:

su rface H10 2. 38 0 su bsurface Hi0 3. 18 0 100 2,4-EIN:

surface H2O 3. 48 0 100 subsurface H1O- 3.08 0 100 Water was then added to submerge the soil under 5 cm. water.

The treatments were carried out when the seedlings reached the height of 1, 3 and 10 cm., respectively. The weedkilling compounds were applied in granular form in amounts corresponding to 0, 2 and 4 kg./ha. of active compound; the biometric values were determined 13 days after .the treatment for the series of 1 cm. seedlings, 14 days after the treatment for the series of 3 cm. seedlings and after 18 days for the series of 10 cm. seedlings.

The results obtained at the end of the test are reported in the Table 4.

Table 4 Height Length of Length of seedlingsin Produetused Dosage, of the epigeous hypogcomparison kgJha. seedlings, part,cm. eons wi From these results the following conclusions can be derived:

First: 2,4-ETN exerts in all cases a greater and faster effect than 2,4-DES. The greatest difierence was found in case of the 3-cm. seedlings, treated with the lesser amounts.

Second: In case of the l0-cm. seedlings, 2,4-ETN applied in the larger amount, damaged the vitality of-almost all seedlings while under the same conditions the action 75 of 2,4-DES was more limited.

EXAMPLE 5 -In a'testcarried out in a conditioned room, reproducing the daily average variations of temperature which occur in the rice field shortly before sowing, the action persist- At the end of the test, the rice and Panicum crus-galli plants were recovered and their biometric values determined. These values are reported in the following table:

ency of 2,4-DES and 2,4-ETN in the steeping water of treated soil was determined. In a series of glass pots containing sieved soil, the soil was submerged under cm. water. Immediately thereafter, the treatment was car- From these experiments it is evident that 2,4-ETN has a more intensive action than 2,4-DES on Panicum crusgalli and does not exert any dangerous influence on rice, while 2,4-DES depresses the growth of rice plants to ried out with both products, which were applied in form a substantial degree.

of a granular composition containing a fertilizer, in amounts corresponding to 4 kg./ha. All pots were incubated at +8 C. (lowest nightly temperature) and at +20 C. (highest day temperature). 5 days after this treatment, the steeping water was removed and replaced with the same quantity of fresh water of 20 C.

The activity of the first steeping water, before the substitution, and of the second steeping water, withdrawn from 19 to 27 days after the treatment, was tested on Panicum crus-galli seeds in a germination box.

The results of these germination tests are reported in Table 5.

Table 5 Sample of first steeping water Sample of final steeping water withdrawnwithdrawn 1 h. before replacement 19 days after the treatment 27 days after the treatment eplgeous hy- Percent epigeous hy- Percent epigeous hy- Pereen part pogeous abpart pogeous abpart pogeous ab- (cm.) part normal (0111.) part normal (cm) part normal (0111.) seedlings (cm) seedlings (cm.) seedlings The foregoing results permit the conclusion that, upon replacing the steeping water, 2,4-ETN is removed at a larger extent than 2,4-DES.

EXAMPLE 6 In this test the weed killing activity and the action persistency of 2,4-DES and of 2,4-E'I'N have been evaluated at conditions similar to these occurring during the sowing of rice fields.

Into a series of pots containing sieved soil, water was introduced up to a height of about 12 cm. 200 seeds of Panicum crus-galli were sown in each pot. When the seedlings reached an average height of 3 cm., they were treated with the two weed killing compounds in a granular formulation with a fertilizer, using amounts corresponding to 4 kg./ha. of active product. 6 days after the treatment, the steeping water was removed and substituted with water at 20 C. seeds of rice were immediately sown in each pot.

During the experiment the incubation temperature was raised from 8 C. to 14 C. (lowest night temperature) and from 20 to 24 C. (highest day temperature).

2. In the art of submerged aqueous rice field culture, the improvement comprising suppressing the growth of the weed Panicum crus-galli by distributing 2,4-dichlorophenoxyethanol over the field in granular form, the said ethanol remaining concentrated within the top layers of the submerged soil which contains the seeds of said weed that germinate during the season, the amount of said ethanol distributed being from 4 to 5 kilograms per hectare of land surface, the field being subsequently subjected to lavement with water and to sowing of the rice seed.

3. In the art of submerged aqueous rice field culture, the improvement comprising suppressing the growth of weeds by distributing 2,4-dichlorophenoxyethanol over the field in granular form, the said ethanol being concentrated within the top layers of the submerged soil which contains the weed seeds, the amount of said ethanol distributed being from 4 to 5 kilograms per hectare of land surface, the field being subsequently subjected to lavement with water and to sowing of the rice seed.

(References on following page) References Cited in the file of this patent FOREIGN PATENTS UNITED STATES PATENTS 574,995 Great Britain Jan. 30, 1946 Mullison Oct. 20, 1953 OTHER REFERENCES Ryker et a1. May 31, 1955 5 Ahlgren et a1: Principles of Weed Control, publ. Swezey July 12, 1955 by I. Wiley and Sons, New York, 1951, page 137. Swezey July 26, 1955 Vlitos et 211.: In Nature, No. 4351, Mar. 21, 1953, Lambrech Oct. 2, 1956 page 523. 

1. IN THE ART OF SUBMERGED AQUEOUS RICE FIELD CULTURE, THE IMPROVEMENT COMPRISING SUPPRESSING THE GROWTH OF THE WEED PANICUM CRUS-GALLI BY DISTRIBUTING 2,4-DICHLOROPHENOXYETHANOL OVER THE FIELD IN GRANULAR FORM, THE SAID ETHANOL REMAINING CONCENTRATED WITHIN THE TOP LAYERS OF THE SUBMERGED SOIL WHICH CONTAINS THE SEEDS OF SAID WEED THAT GERMINATE DURING THE SEASON, THE AMOUNT OF SAID ETHANOL DISTRIBUTED BEING FROM 4 TO BELOW 10 KILOGRAMS PER HECTARE OF LAND SURFACE, THE FIELD BEING SUBSEQUENTLY SUBJECTED TO LAVEMENT WITH WATER AND TO SOWING OF THE RICE SEED. 